Difficulty: Easy
Correct Answer: Efficient use of fuel
Explanation:
Introduction / Context:
Stack loss represents sensible and chemical heat carried away by flue gases. Minimizing it is a key lever to improve furnace economy. Operators track stack temperature and oxygen/CO to infer excess air and heat recovery effectiveness.
Given Data / Assumptions:
Concept / Approach:
Low stack loss means lower flue-gas temperature and/or optimized excess air, hence a larger fraction of fuel energy is transferred to the load rather than exhausted. While too little air can create unburned fuel or CO losses, the question focuses on the general interpretation: low stack loss correlates with better fuel utilization when combustion is adequate.
Step-by-Step Solution:
Verification / Alternative check:
Combustion calculators show that reducing excess air from very high values to optimal ranges cuts stack losses while maintaining complete combustion (low CO).
Why Other Options Are Wrong:
Common Pitfalls:
Equating low O2 with efficiency; true efficiency needs both adequate combustion and low exhaust temperature.
Final Answer:
Efficient use of fuel
Discussion & Comments